Disclosed in JP2008-18898A is an electric parking brake apparatus having an emergency release function for a vehicle (which will be hereinafter referred to as an electric parking brake apparatus) that includes an actuator and an emergency release mechanism. The actuator includes a driven member (an output gear), which is configured so as to control a parking brake to be in an actuated state (i.e. a braked state, a locked state), where the parking brake is actuated, and in a released state (i.e. a lock released state), where the parking brake is not actuated, in response to a driving of an electric motor. The emergency release mechanism is configured so as to be operated from a vehicle interior. More specifically, the emergency release mechanism is configured so as to release the parking brake without relying on the driving of the electric motor in a case of emergency. Furthermore, the emergency release mechanism includes an emergency driving member (an emergency release gear) and an operation mechanism. The emergency driven member, which is provided within the actuator, is configured so as to drive the driven member (the output gear). The operation mechanism is provided between an operation portion, which is provided within the vehicle interior, and the actuator and is configured so as to drive the emergency driving member (the emergency release gear).
According to the electric parking brake apparatus disclosed in JP2008-18898A, the emergency release mechanism further includes a driving force transmitting member (a rotation transmitting member), which is configured to be manually operated from the vehicle interior, so that the driven member (the output gear) provided within the actuator is driven by means of the driving force transmitting member (the rotation transmitting member) in order to release (unlock) the electric parking brake apparatus.
The driving force transmitting member of the emergency release mechanism of the electric parking brake apparatus disclosed in JP2008-18898A includes a rotating shaft, a hexagon socket head and an emergency output gear. The rotating shaft is configured so as to be manually and rotatably operated by means of a tool from the vehicle interior and is configured to be curvable. The hexagon socket head is fixed at an input end portion of the rotating shaft (i.e. an end portion of the rotating shaft positioned closer to the vehicle interior) and is configured so that the tool is attached to and detached from the hexagon socket head. The emergency output gear is fixed at an output end portion of the rotating shaft (i.e. an end portion of the rotating shaft positioned closer to the actuator) and normally engages with the driven member (the output gear). According to the driving force transmitting member of the emergency release mechanism disclosed in JP2008-18898A, the hexagon socket head and the rotating shaft may be driven in addition to the emergency output gear in a case where the driven member (the output gear) of the actuator is driven by the electric motor in a normal use. As a result, an operating noise may be generated, which may cause a discomfort to a driver.
Illustrated in FIG. 52 is another example of an electric parking brake apparatus having an emergency release function for a vehicle, which may be conceivable on the basis of the electric parking brake apparatus disclosed in JP2008-18898A. As illustrated in FIG. 52, the electric parking brake apparatus includes an operation mechanism 4, which is disposed between an operation portion 1 provided at a vehicle interior and an actuator 2 and which is configured so as to drive an emergency driving gear 3 (an emergency release gear). More specifically, the operation mechanism 4 includes an operation driving member 4a (a cable-type driving shaft), an outer tube 4b and a positioning spring 4c. The operation driving member 4a is configured so as to be movable (advance and withdraw) relative to the emergency driving member 3 and so as to be engaged with and disengaged from the emergency driving member 3 (i.e. so that a torque is transmittable and not transmittable). More specifically, the operation driving member 4a is configured so as to drive the emergency driving member 3 in a case where the operation driving member 4a is engaged with the emergency driving member 3 (in a case where the torque is transmittable is established). The outer tube 4b accommodates therein the operation driving member 4a. The positioning spring 4c normally retains the operation driving member 4a to be disengaged from the emergency driving member 3 (i.e. in a state where the torque is not transmittable). Accordingly to an emergency release mechanism of the electric parking brake apparatus illustrated in FIG. 52, the operation driving member 4a of the operation mechanism 4 is not driven in a case where a driven member 5 (an output gear), which is provided within the actuator 2, is driven by an electric motor 6 in the normal use. As a result, an operation noise may be reduced.
However, according to the operation mechanism 4 illustrated in FIG. 52, a stroke necessary for moving a gear connecting portion 4a1 of the operation driving member 4a from a withdrawal position illustrated in FIG. 52 to an engaged position where the gear connecting portion 4a1 is engaged with a shaft bore 3a of the emergency driving member 3 so that the torque is transmittable may largely differ depending on variations of length of the operation driving member 4a, variations of length of the outer tube 4b, variations of arrangement of the operation driving member 4a and the outer tube 4b to the vehicle, and the like. As a result, an engagement amount (a connecting amount) of the gear connecting portion 4a1 relative to the emergency driving member 3 may become insufficient, or the gear connecting portion 4a1 may not be engaged with the emergency driving member 3.
A need thus exists to provide an electric parking brake apparatus having an emergency release function for a vehicle, which is not susceptible to the drawback mentioned above.